when so made, the connexion of our own countryman with this important question is but little known, and rarely mentioned even among ourselves.

That geographical and geometric lines should have formed the divisions of the original provinces, and thus of the States, has exercised an influence upon the destinies of our country, which is not the less evident, because it has rarely been noticed. In most of the disputes concerning land titles derived from different authorities, or concerning territorial jurisdiction, it has not been necessary to have recourse to civil violence or hostile arms. The ultima ratio has been not the cannon or the bayonet, but the plumb-line, the clock, and the telescope. Even courts of civil authority, where such have had jurisdiction, have been appealed to, only to cause one or other party to perform his duty, or to commission the astronomic surveyors by whom the determination was made. The habit has thus been created of referring to reason and science for the composition of all disputes; and this is so firmly established among the people, that even the folly of their rulers, as was manifested in a recent instance, cannot bring them to refer the matter to the decision of arms. That this habit has become a part of the character of our people, is in a great measure due to the confidence created

by the fidelity and accuracy with which the earliest operations of the sort were performed. From the delineation of Mason and Dixon's line to the present time, both State governments, although this portion of their sovereignty has been reserved, and individuals, who have occasionally suffered hardship, have bowed in obedience to the decision of the astronomer. Rittenhouse was the first American, who was employed in the delineation of such lines; he was also most extensively engaged in tracing them, and, with those formed under his instruction, actually defined nearly all the important division lines within the chartered limits of the thirteen original States. Most of these delicate and valuable operations were however performed at a later period of his life, and after the close of the revolutionary war. The account of them will therefore fall into a subsequent chapter of this memoir. One alone is connected by date with that of which we have just spoken.

This was the determination of the division line between New York and New Jersey, and thus of the point whence the parallel, which divides the former State from Pennsylvania, was to be traced westward. The northern limit of New Jersey upon Hudson's River is the forty-first degree of latitude. The point where this parallel intersects the shore was fixed by Rittenhouse in

the year 1769, at the request of a board of commissioners deriving their authority from the legislatures of the provinces of New York and New Jersey. The northern limit of both Pennsylvania and New Jersey, upon the Delaware, is the fortysecond degree of latitude; and this parallel, continued westward, divides the former from New York. To determine the place where this parallel intersects the Delaware, Rittenhouse received the appointment of commissioner from his native province, and was met by a gentleman named on the part of the province of New York. This appointment also included the duty of running the parallel westward, but nothing farther was done at the time (1774), than to determine the point of departure upon the Delaware.

eter.

Experiments on the Compressibility of

Water. Adaptation of Planetary Machines to Clocks. Project of an Orrery.

For the sake of connecting with each other the geodetic operations of Rittenhouse performed previous to the revolutionary war, we have departed from the order of time. We shall now return, for the purpose of mentioning various other scientific occupations in which he was engaged, between the date at which he was first employed upon the boundary of Maryland, and that at which he became a commissioner to define the line between the States of New York and Pennsylvania.

To a person engaged in the manufacture of clocks, and occupied in determining their rates by astronomic observations, the influence of variations of temperature upon the oscillations of pendulums becomes at once apparent. That this is owing to the expansion and contraction of the materials of which the pendulums are composed, under alternations of heat and cold, was well

understood. Partial remedies, too, had been applied; but they had not yet been rendered as available as they might be, for want of a sufficient number of well-conducted experiments. If such had been made, they had not been recorded or published. At the present time, we can refer to no observations of earlier date than those of Rittenhouse, which are worthy of confidence, except a few of Muschenbroeck and of Smeaton. The latter were only made public in 1754, when we have reason to believe that Rittenhouse had already made some progress in his researches. That he entered into this investigation experimentally and pursued it with no small success, we have abundant evidence. The first volume of the "Transactions of the American Philosophical Society," published in 1770, contains a paper of his on expansion by heat; another paper on the same subject is noted by Rush as existing in their archives, and is probably that on the improvement of timekeepers, in the fourth volume. The accuracy of his experiments is demonstrated by the various astronomic clocks, which were constructed by his own hands, or under his direction, in which original forms of compensation pendulumś were employed. In this respect, Rittenhouse was somewhat in advance of the applications of science in Europe. The mercurial pendulum, which is now admitted to be the best